Sidelink beam failure detection

ABSTRACT

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a first node may transmit, to a second node on a beamformed link from the first node to the second node, a first signal, wherein the first node and the second node are associated with common timing; determine whether a second signal, based at least in part on the first signal, is received on a beamformed link from the second node to the first node; and transmit a third signal based at least in part on receiving the second signal or perform a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received. Numerous other aspects are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This Patent Application claims priority to U.S. Provisional PatentApplication No. 62,969,544, filed on Feb. 3, 2020, entitled “SIDELINKBEAM FAILURE DETECTION,” and assigned to the assignee hereof. Thedisclosure of the prior Application is considered part of and isincorporated by reference into this Patent Application.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wirelesscommunication and to techniques and apparatuses for sidelink beamfailure detection.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power, and/or the like). Examples of such multiple-accesstechnologies include code division multiple access (CDMA) systems, timedivision multiple access (TDMA) systems, frequency-division multipleaccess (FDMA) systems, orthogonal frequency-division multiple access(OFDMA) systems, single-carrier frequency-division multiple access(SC-FDMA) systems, time division synchronous code division multipleaccess (TD-SCDMA) systems, and Long Term Evolution (LTE).LTE/LTE-Advanced is a set of enhancements to the Universal MobileTelecommunications System (UMTS) mobile standard promulgated by theThird Generation Partnership Project (3GPP).

A wireless communication network may include a number of base stations(BSs) that can support communication for a number of user equipment(UEs). A UE may communicate with a BS via the downlink and uplink. Thedownlink (or forward link) refers to the communication link from the BSto the UE, and the uplink (or reverse link) refers to the communicationlink from the UE to the BS. As will be described in more detail herein,a BS may be referred to as a Node B, a gNB, an access point (AP), aradio head, a transmit receive point (TRP), a New Radio (NR) BS, a 5GNode B, and/or the like.

The above multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent user equipment to communicate on a municipal, national,regional, and even global level. NR, which may also be referred to as5G, is a set of enhancements to the LTE mobile standard promulgated bythe 3GPP. NR is designed to better support mobile broadband Internetaccess by improving spectral efficiency, lowering costs, improvingservices, making use of new spectrum, and better integrating with otheropen standards using orthogonal frequency division multiplexing (OFDM)with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL), using CP-OFDMand/or SC-FDM (e.g., also known as discrete Fourier transform spreadOFDM (DFT-s-OFDM)) on the uplink (UL), as well as supportingbeamforming, multiple-input multiple-output (MIMO) antenna technology,and carrier aggregation. However, as the demand for mobile broadbandaccess continues to increase, there exists a need for furtherimprovements in LTE and NR technologies. Preferably, these improvementsshould be applicable to other multiple access technologies and thetelecommunication standards that employ these technologies.

SUMMARY

In some aspects, a method of wireless communication, performed by afirst node, may include transmitting, to a second node on a beamformedlink from the first node to the second node, a first signal, wherein thefirst node and the second node are associated with common timing;determining whether a second signal, based at least in part on the firstsignal, is received on a beamformed link from the second node to thefirst node; and transmitting a third signal on the beamformed link fromthe first node to the second node based at least in part on receivingthe second signal, or performing a sidelink beam failure recoveryprocedure based at least in part on determining that the second signalis not received.

In some aspects, a method of wireless communication, performed by asecond node, may include determining whether a first signal is receivedfrom a first node on a beamformed link from the first node to the secondnode, wherein the first node and the second node are associated withcommon timing; determining whether to transmit, on a beamformed linkfrom the second node to the first node, a second signal based at leastin part on whether the first signal is received; and receiving a thirdsignal based at least in part on the second signal, or performing asidelink beam failure recovery procedure based at least in part onfailing to receive the first signal or the third signal.

In some aspects, a first node for wireless communication may include amemory and one or more processors operatively coupled to the memory. Thememory and the one or more processors may be configured to transmit, toa second node on a beamformed link from the first node to the secondnode, a first signal, wherein the first node and the second node areassociated with common timing; determine whether a second signal, basedat least in part on the first signal, is received on a beamformed linkfrom the second node to the first node; and transmit a third signalbased at least in part on receiving the second signal, or perform asidelink beam failure recovery procedure based at least in part ondetermining that the second signal is not received.

In some aspects, a second node for wireless communication may include amemory and one or more processors operatively coupled to the memory. Thememory and the one or more processors may be configured to determinewhether a first signal is received from a first node on a beamformedlink from the first node to the second node, wherein the first node andthe second node are associated with common timing; determine whether totransmit, on a beamformed link from the second node to the first node, asecond signal based at least in part on whether the first signal isreceived; and receive a third signal based at least in part on thesecond signal, or perform a sidelink beam failure recovery procedurebased at least in part on failing to receive the first signal or thethird signal.

In some aspects, a non-transitory computer-readable medium may store oneor more instructions for wireless communication. The one or moreinstructions, when executed by one or more processors of a first node,may cause the one or more processors to transmit, to a second node on abeamformed link from the first node to the second node, a first signal,wherein the first node and the second node are associated with commontiming; determine whether a second signal, based at least in part on thefirst signal, is received on a beamformed link from the second node tothe first node; and transmit a third signal based at least in part onreceiving the second signal, or perform a sidelink beam failure recoveryprocedure based at least in part on determining that the second signalis not received.

In some aspects, a non-transitory computer-readable medium may store oneor more instructions for wireless communication. The one or moreinstructions, when executed by one or more processors of a second node,may cause the one or more processors to determine whether a first signalis received from a first node on a beamformed link from the first nodeto the second node, wherein the first node and the second node areassociated with common timing; determine whether to transmit, on abeamformed link from the second node to the first node, a second signalbased at least in part on whether the first signal is received; andreceive a third signal based at least in part on the second signal, orperform a sidelink beam failure recovery procedure based at least inpart on failing to receive the first signal or the third signal.

In some aspects, an apparatus for wireless communication may includemeans for transmitting, to a second node on a beamformed link from theapparatus to the second node, a first signal, wherein the apparatus andthe second node are associated with common timing; means for determiningwhether a second signal, based at least in part on the first signal, isreceived on a beamformed link from the second node to the apparatus; andmeans for transmitting a third signal on the beamformed link from thefirst node to the second node based at least in part on receiving thesecond signal or performing a sidelink beam failure recovery procedurebased at least in part on determining that the second signal is notreceived.

In some aspects, an apparatus for wireless communication may includemeans for determining whether a first signal is received from a firstnode on a beamformed link from the first node to the apparatus, whereinthe first node and the apparatus are associated with common timing;means for determining whether to transmit, on a beamformed link from theapparatus to the first node, a second signal based at least in part onwhether the first signal is received; and means for receiving a thirdsignal based at least in part on the second signal; or means forperforming a sidelink beam failure recovery procedure based at least inpart on failing to receive the first signal or the third signal.

Aspects generally include a method, apparatus, system, computer programproduct, non-transitory computer-readable medium, user equipment, basestation, wireless communication device, and/or processing system assubstantially described herein with reference to and as illustrated bythe drawings.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter. The conceptionand specific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the scope of the appended claims. Characteristics of theconcepts disclosed herein, both their organization and method ofoperation, together with associated advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. Each of the figures is provided for the purposesof illustration and description, and not as a definition of the limitsof the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above-recited features of the present disclosure can beunderstood in detail, a more particular description, briefly summarizedabove, may be had by reference to aspects, some of which are illustratedin the appended drawings. It is to be noted, however, that the appendeddrawings illustrate only certain typical aspects of this disclosure andare therefore not to be considered limiting of its scope, for thedescription may admit to other equally effective aspects. The samereference numbers in different drawings may identify the same or similarelements.

FIG. 1 is a block diagram illustrating an example of a wirelesscommunication network, in accordance with various aspects of the presentdisclosure.

FIG. 2 is a block diagram illustrating an example of a base station incommunication with a UE in a wireless communication network, inaccordance with various aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example of sidelink communications,in accordance with various aspects of the present disclosure.

FIG. 4 is a diagram illustrating an example of sidelink communicationsand access link communications, in accordance with various aspects ofthe present disclosure.

FIGS. 5-8 are diagrams illustrating examples of sidelink beam failuredetection and recovery, in accordance with various aspects of thepresent disclosure.

FIGS. 9 and 10 are diagrams illustrating example processes performed,for example, by a user equipment, in accordance with various aspects ofthe present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented withreference to various apparatuses and techniques. These apparatuses andtechniques will be described in the following detailed description andillustrated in the accompanying drawings by various blocks, modules,components, circuits, steps, processes, algorithms, and/or the like(collectively referred to as “elements”). These elements may beimplemented using hardware, software, or combinations thereof. Whethersuch elements are implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem.

It should be noted that while aspects may be described herein usingterminology commonly associated with a 5G or NR radio access technology(RAT), aspects of the present disclosure can be applied to other RATs,such as a 3G RAT, a 4G RAT, and/or a RAT subsequent to 5G (e.g., 6G).

FIG. 1 is a diagram illustrating a wireless network 100 in which aspectsof the present disclosure may be practiced. The wireless network 100 maybe an LTE network or some other wireless network, such as a 5G or NRnetwork. The wireless network 100 may include a number of BSs 110 (shownas BS 110 a, BS 110 b, BS 110 c, and BS 110 d) and other networkentities. A BS is an entity that communicates with user equipment (UEs)and may also be referred to as a base station, a NR BS, a Node B, a gNB,a 5G node B (NB), an access point, a transmit receive point (TRP),and/or the like. Each BS may provide communication coverage for aparticular geographic area. In 3GPP, the term “cell” can refer to acoverage area of a BS and/or a BS subsystem serving this coverage area,depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or another type of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a closed subscriber group (CSG)). ABS for a macro cell may bereferred to as a macro BS. ABS for a pico cell may be referred to as apico BS. A BS for a femto cell may be referred to as a femto BS or ahome BS. In the example shown in FIG. 1, a BS 110 a may be a macro BSfor a macro cell 102 a, a BS 110 b may be a pico BS for a pico cell 102b, and a BS 110 c may be a femto BS for a femto cell 102 c. A BS maysupport one or multiple (e.g., three) cells. The terms “eNB”, “basestation”, “NR BS”, “gNB”, “TRP”, “AP”, “node B”, “5G NB”, and “cell” maybe used interchangeably herein.

In some aspects, a cell may not necessarily be stationary, and thegeographic area of the cell may move according to the location of amobile BS. In some aspects, the BSs may be interconnected to one anotherand/or to one or more other BSs or network nodes (not shown) in thewireless network 100 through various types of backhaul interfaces suchas a direct physical connection, a virtual network, and/or the likeusing any suitable transport network.

Wireless network 100 may also include relay stations. A relay station isan entity that can receive a transmission of data from an upstreamstation (e.g., a BS or a UE) and send a transmission of the data to adownstream station (e.g., a UE or a BS). A relay station may also be aUE that can relay transmissions for other UEs. In the example shown inFIG. 1, a relay BS 110 d may communicate with macro BS 110 a and a UE120 d in order to facilitate communication between BS 110 a and UE 120d. A relay BS may also be referred to as a relay station, a relay basestation, a relay, and/or the like.

Wireless network 100 may be a heterogeneous network that includes BSs ofdifferent types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/orthe like. These different types of BSs may have different transmit powerlevels, different coverage areas, and different impacts on interferencein wireless network 100. For example, macro BSs may have a high transmitpower level (e.g., 5 to 40 watts) whereas pico BSs, femto BSs, and relayBSs may have lower transmit power levels (e.g., 0.1 to 2 watts).

A network controller 130 may couple to a set of BSs and may providecoordination and control for these BSs. Network controller 130 maycommunicate with the BSs via a backhaul. The BSs may also communicatewith one another, e.g., directly or indirectly via a wireless orwireline backhaul.

UEs 120 (e.g., 120 a, 120 b, 120 c) may be dispersed throughout wirelessnetwork 100, and each UE may be stationary or mobile. A UE may also bereferred to as an access terminal, a terminal, a mobile station, asubscriber unit, a station, and/or the like. A UE may be a cellularphone (e.g., a smart phone), a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, a camera, a gaming device, a netbook, a smartbook, anultrabook, a medical device or equipment, biometric sensors/devices,wearable devices (smart watches, smart clothing, smart glasses, smartwrist bands, smart jewelry (e.g., smart ring, smart bracelet)), anentertainment device (e.g., a music or video device, or a satelliteradio), a vehicular component or sensor, smart meters/sensors,industrial manufacturing equipment, a global positioning system device,or any other suitable device that is configured to communicate via awireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolvedor enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEsinclude, for example, robots, drones, remote devices, sensors, meters,monitors, location tags, and/or the like, that may communicate with abase station, another device (e.g., remote device), or some otherentity. A wireless node may provide, for example, connectivity for or toa network (e.g., a wide area network such as Internet or a cellularnetwork) via a wired or wireless communication link. Some UEs may beconsidered Internet-of-Things (IoT) devices, and/or may be implementedas NB-IoT (narrowband internet of things) devices. Some UEs may beconsidered a Customer Premises Equipment (CPE). UE 120 may be includedinside a housing that houses components of UE 120, such as processorcomponents, memory components, and/or the like.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,and/or the like. A frequency may also be referred to as a carrier, afrequency channel, and/or the like. Each frequency may support a singleRAT in a given geographic area in order to avoid interference betweenwireless networks of different RATs. In some cases, NR or 5G RATnetworks may be deployed.

In some aspects, two or more UEs 120 (e.g., shown as UE 120 a and UE 120e) may communicate directly using one or more sidelink channels (e.g.,without using a base station 110 as an intermediary to communicate withone another). For example, the UEs 120 may communicate usingpeer-to-peer (P2P) communications, device-to-device (D2D)communications, a vehicle-to-everything (V2X) protocol (e.g., which mayinclude a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure(V2I) protocol, and/or the like), a mesh network, and/or the like. Inthis case, the UE 120 may perform scheduling operations, resourceselection operations, and/or other operations described elsewhere hereinas being performed by the base station 110.

Devices of wireless network 100 may communicate using theelectromagnetic spectrum, which may be subdivided based on frequency orwavelength into various classes, bands, channels, or the like. Forexample, devices of wireless network 100 may communicate using anoperating band having a first frequency range (FR1), which may span from410 MHz to 7.125 GHz, and/or may communicate using an operating bandhaving a second frequency range (FR2), which may span from 24.25 GHz to52.6 GHz. The frequencies between FR1 and FR2 are sometimes referred toas mid-band frequencies. Although a portion of FR1 is greater than 6GHz, FR1 is often referred to as a “sub-6 GHz” band. Similarly, FR2 isoften referred to as a “millimeter wave” band despite being differentfrom the extremely high frequency (EHF) band (30 GHz-300 GHz) which isidentified by the International Telecommunications Union (ITU) as a“millimeter wave” band. Thus, unless specifically stated otherwise, itshould be understood that the term “sub-6 GHz” or the like, if usedherein, may broadly represent frequencies less than 6 GHz, frequencieswithin FR1, and/or mid-band frequencies (e.g., greater than 7.125 GHz).Similarly, unless specifically stated otherwise, it should be understoodthat the term “millimeter wave” or the like, if used herein, may broadlyrepresent frequencies within the EHF band, frequencies within FR2,and/or mid-band frequencies (e.g., less than 24.25 GHz). It iscontemplated that the frequencies included in FR1 and FR2 may bemodified, and techniques described herein are applicable to thosemodified frequency ranges.

As indicated above, FIG. 1 is provided as an example. Other examples maydiffer from what is described with regard to FIG. 1.

FIG. 2 shows a block diagram of a design 200 of base station 110 and UE120, which may be one of the base stations and one of the UEs in FIG. 1.Base station 110 may be equipped with T antennas 234 a through 234 t,and UE 120 may be equipped with R antennas 252 a through 252 r, where ingeneral T≥1 and R≥1.

At base station 110, a transmit processor 220 may receive data from adata source 212 for one or more UEs, select one or more modulation andcoding schemes (MCS) for each UE based at least in part on channelquality indicators (CQIs) received from the UE, process (e.g., encodeand modulate) the data for each UE based at least in part on the MCS(s)selected for the UE, and provide data symbols for all UEs. Transmitprocessor 220 may also process system information (e.g., for semi-staticresource partitioning information (SRPI) and/or the like) and controlinformation (e.g., CQI requests, grants, upper layer signaling, and/orthe like) and provide overhead symbols and control symbols. Transmitprocessor 220 may also generate reference symbols for reference signals(e.g., the cell-specific reference signal (CRS)) and synchronizationsignals (e.g., the primary synchronization signal (PSS) and secondarysynchronization signal (SSS)). A transmit (TX) multiple-inputmultiple-output (MIMO) processor 230 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, the overheadsymbols, and/or the reference symbols, if applicable, and may provide Toutput symbol streams to T modulators (MODs) 232 a through 232 t. Eachmodulator 232 may process a respective output symbol stream (e.g., forOFDM and/or the like) to obtain an output sample stream. Each modulator232 may further process (e.g., convert to analog, amplify, filter, andupconvert) the output sample stream to obtain a downlink signal. Tdownlink signals from modulators 232 a through 232 t may be transmittedvia T antennas 234 a through 234 t, respectively. According to variousaspects described in more detail below, the synchronization signals canbe generated with location encoding to convey additional information.

At UE 120, antennas 252 a through 252 r may receive the downlink signalsfrom base station 110 and/or other base stations and may providereceived signals to demodulators (DEMODs) 254 a through 254 r,respectively. Each demodulator 254 may condition (e.g., filter, amplify,downconvert, and digitize) a received signal to obtain input samples.Each demodulator 254 may further process the input samples (e.g., forOFDM and/or the like) to obtain received symbols. A MIMO detector 256may obtain received symbols from all R demodulators 254 a through 254 r,perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive processor 258 may process (e.g.,demodulate and decode) the detected symbols, provide decoded data for UE120 to a data sink 260, and provide decoded control information andsystem information to a controller/processor 280. A channel processormay determine reference signal received power (RSRP), received signalstrength indicator (RSSI), reference signal received quality (RSRQ),channel quality indicator (CQI), and/or the like. In some aspects, oneor more components of UE 120 may be included in a housing.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data from a data source 262 and control information (e.g., forreports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) fromcontroller/processor 280. Transmit processor 264 may also generatereference symbols for one or more reference signals. The symbols fromtransmit processor 264 may be precoded by a TX MIMO processor 266 ifapplicable, further processed by modulators 254 a through 254 r (e.g.,for DFT-s-OFDM, CP-OFDM, and/or the like), and transmitted to basestation 110. At base station 110, the uplink signals from UE 120 andother UEs may be received by antennas 234, processed by demodulators232, detected by a MIMO detector 236 if applicable, and furtherprocessed by a receive processor 238 to obtain decoded data and controlinformation sent by UE 120. Receive processor 238 may provide thedecoded data to a data sink 239 and the decoded control information tocontroller/processor 240. Base station 110 may include communicationunit 244 and communicate to network controller 130 via communicationunit 244. Network controller 130 may include communication unit 294,controller/processor 290, and memory 292.

Controller/processor 240 of base station 110, controller/processor 280of UE 120, and/or any other component(s) of FIG. 2 may perform one ormore techniques associated with sidelink beam failure detection, asdescribed in more detail elsewhere herein. For example,controller/processor 240 of base station 110, controller/processor 280of UE 120, and/or any other component(s) of FIG. 2 may perform or directoperations of, for example, process 900 of FIG. 9, process 1000 of FIG.10, and/or other processes as described herein. Memories 242 and 282 maystore data and program codes for base station 110 and UE 120,respectively. In some aspects, memory 242 and/or memory 282 may comprisea non-transitory computer-readable medium storing one or moreinstructions for wireless communication. For example, the one or moreinstructions, when executed by one or more processors of the basestation 110 and/or the UE 120, may perform or direct operations of, forexample, process 900 of FIG. 9, process 1000 of FIG. 10, and/or otherprocesses as described herein. A scheduler 246 may schedule UEs for datatransmission on the downlink and/or uplink.

In some aspects, a node (e.g., UE 120 or BS 110) may include means fortransmitting, to a second node on a beamformed link from the first nodeto the second node, a first signal; means for determining whether asecond signal, based at least in part on the first signal, is receivedon a beamformed link from the second node to the first node; means fortransmitting a third signal on the beamformed link from the first nodeto the second node based at least in part on receiving the secondsignal; means for performing a sidelink beam failure recovery procedurebased at least in part on determining that the second signal is notreceived; means for determining whether a first signal is received froma first node on a beamformed link from the first node to the secondnode; means for determining whether to transmit, on a beamformed linkfrom the second node to the first node, a second signal based at leastin part on whether the first signal is received; means for receiving athird signal based at least in part on the second signal; means forperforming a sidelink beam failure recovery procedure based at least inpart on failing to receive the first signal or the third signal; meansfor performing the sidelink beam failure recovery procedure based atleast in part on failing to receive one or more of the first signal orthe third signal a threshold number of times; and/or the like. In someaspects, such means may include one or more components of UE 120 or BS110 described in connection with FIG. 2, such as controller/processor280, transmit processor 264, TX MIMO processor 266, MOD 254, antenna252, DEMOD 254, MIMO detector 256, receive processor 258, antenna 234,DEMOD 232, MIMO detector 236, receive processor 238,controller/processor 240, transmit processor 220, TX MIMO processor 230,MOD 232, antenna 234, and/or the like.

As indicated above, FIG. 2 is provided as an example. Other examples maydiffer from what is described with regard to FIG. 2.

FIG. 3 is a diagram illustrating an example 300 of sidelinkcommunications, in accordance with various aspects of the presentdisclosure.

As shown in FIG. 3, a first UE 305-1 may communicate with a second UE305-2 (and one or more other UEs 305) via one or more sidelink channels310. The UEs 305-1 and 305-2 may communicate using the one or moresidelink channels 310 for P2P communications, D2D communications, V2Xcommunications (e.g., which may include V2V communications, V2Icommunications, V2P communications, and/or the like), mesh networking,and/or the like. In some aspects, the UEs 305 (e.g., UE 305-1 and/or UE305-2) may correspond to one or more other UEs described elsewhereherein, such as UE 120. In some aspects, the one or more sidelinkchannels 310 may use a ProSe sidelink (PC5) interface and/or may operatein a high frequency band (e.g., the 5.9 GHz band). Additionally, oralternatively, the UEs 305 may synchronize timing of transmission timeintervals (TTIs) (e.g., frames, subframes, slots, symbols, and/or thelike) using global navigation satellite system (GNSS) timing or timingof a base station 110 associated with one or more of the UEs 305.

As further shown in FIG. 3, the one or more sidelink channels 310 mayinclude a physical sidelink control channel (PSCCH) 315, a physicalsidelink shared channel (PSSCH) 320, and/or a physical sidelink feedbackchannel (PSFCH) 325. The PSCCH 315 may be used to communicate controlinformation, similar to a physical downlink control channel (PDCCH)and/or a physical uplink control channel (PUCCH) used for cellularcommunications with a base station 110 via an access link or an accesschannel. The PSSCH 320 may be used to communicate data, similar to aphysical downlink shared channel (PDSCH) and/or a physical uplink sharedchannel (PUSCH) used for cellular communications with a base station 110via an access link or an access channel. For example, the PSCCH 315 maycarry sidelink control information (SCI) 330, which may indicate variouscontrol information used for sidelink communications, such as one ormore resources (e.g., time resources, frequency resources, spatialresources, and/or the like) where a transport block (TB) 335 may becarried on the PSSCH 320. The TB 335 may include data. The PSFCH 325 maybe used to communicate sidelink feedback 340, such as hybrid automaticrepeat request (HARQ) feedback (e.g., acknowledgement or negativeacknowledgement (ACK/NACK) information), transmit power control (TPC), ascheduling request (SR), and/or the like.

In some aspects, the one or more sidelink channels 310 may use resourcepools. For example, a scheduling assignment (e.g., included in SCI 330)may be transmitted in sub-channels using specific resource blocks (RBs)across time. In some aspects, data transmissions (e.g., on the PSSCH320) associated with a scheduling assignment may occupy adjacent RBs inthe same subframe as the scheduling assignment (e.g., using frequencydivision multiplexing). In some aspects, a scheduling assignment andassociated data transmissions are not transmitted on adjacent RBs.

In some aspects, a UE 305 may operate using a transmission mode whereresource selection and/or scheduling is performed by the UE 305 (e.g.,rather than a base station 110). In some aspects, the UE 305 may performresource selection and/or scheduling by sensing channel availability fortransmissions. For example, the UE 305 may measure a received signalstrength indicator (RSSI) parameter (e.g., a sidelink-RSSI (S-RSSI)parameter) associated with various sidelink channels, may measure areference signal received power (RSRP) parameter (e.g., a PSSCH-RSRPparameter) associated with various sidelink channels, may measure areference signal received quality (RSRQ) parameter (e.g., a PSSCH-RSRQparameter) associated with various sidelink channels, and/or the like,and may select a channel for transmission of a sidelink communicationbased at least in part on the measurement(s).

Additionally, or alternatively, the UE 305 may perform resourceselection and/or scheduling using SCI 330 received in the PSCCH 315,which may indicate occupied resources, channel parameters, and/or thelike. Additionally, or alternatively, the UE 305 may perform resourceselection and/or scheduling by determining a channel busy rate (CBR)associated with various sidelink channels, which may be used for ratecontrol (e.g., by indicating a maximum number of resource blocks thatthe UE 305 can use for a particular set of subframes).

In the transmission mode where resource selection and/or scheduling isperformed by a UE 305, the UE 305 may generate sidelink grants, and maytransmit the grants in SCI 330. A sidelink grant may indicate, forexample, one or more parameters (e.g., transmission parameters) to beused for an upcoming sidelink transmission, such as one or more resourceblocks to be used for the upcoming sidelink transmission on the PSSCH320 (e.g., for TBs 335), one or more subframes to be used for theupcoming sidelink transmission, a modulation and coding scheme (MCS) tobe used for the upcoming sidelink transmission, and/or the like. In someaspects, a UE 305 may generate a sidelink grant that indicates one ormore parameters for semi-persistent scheduling (SPS), such as aperiodicity of a sidelink transmission. Additionally, or alternatively,the UE 305 may generate a sidelink grant for event-driven scheduling,such as for an on-demand sidelink message.

As indicated above, FIG. 3 is provided as an example. Other examples maydiffer from what is described with respect to FIG. 3.

FIG. 4 is a diagram illustrating an example 400 of sidelinkcommunications and access link communications, in accordance withvarious aspects of the present disclosure.

As shown in FIG. 4, a transmitter (Tx) UE 405 and a receiver (Rx) UE 410may communicate with one another via a sidelink, as described above inconnection with FIG. 3. As further shown, in some sidelink modes, a basestation 110 may communicate with the Tx UE 405 via a first access link.Additionally, or alternatively, in some sidelink modes, the base station110 may communicate with the Rx UE 410 via a second access link. The TxUE 405 and/or the Rx UE 410 may correspond to one or more UEs describedelsewhere herein, such as the UE 120 of FIG. 1. Thus, a sidelink mayrefer to a direct link between UEs 120, and an access link may refer toa direct link between a base station 110 and a UE 120. Sidelinkcommunications may be transmitted via the sidelink, and access linkcommunications may be transmitted via the access link. An access linkcommunication may be either a downlink communication (from a basestation 110 to a UE 120) or an uplink communication (from a UE 120 to abase station 110). In some aspects, the UEs 405 and 410 may not beassociated with an access link.

As indicated above, FIG. 4 is provided as an example. Other examples maydiffer from what is described with respect to FIG. 4.

Two nodes may communicate with each other using sidelink communications.A node may be any UE, such as an integrated access and backhaul (IAB)node, a UE associated with vehicular communications, a UE associatedwith a sidelink network, a reduced capability UE, or the like. Asidelink communication involves the transmission or reception of databetween the UEs without an intermediary base station or schedulingentity and without communication of the data via an access link.Sidelink communications may be useful in various applications, such aslow-latency scenarios, poor coverage scenarios, UE-to-network ornetwork-to-UE relaying, vehicle-to-anything communication,vehicle-to-vehicle communication, and so on. Nodes may use beamformingto communicate with each other on the sidelink, which may improve radioperformance of the nodes while using less power than an omni-directionalor pseudo-omni-directional transmission with equivalent range.

In some cases, a beam on a beamformed sidelink may fail, meaning thatthe beam no longer provides a link to another node. For example, ablocker may move into the propagation path of the beam, or the nodetransmitting or receiving the beam may move, thereby causing failure ofthe sidelink. In this case, the beamformed sidelink may experiencediminished performance or may fail. This may lead to interruptedcommunications, wasted resources, diminished throughput, and so on.Furthermore, detecting a failed beam on a sidelink in an expeditiousfashion may be difficult if there is no central scheduler associatedwith the sidelink to arrange the transmission of signals or beam failurerecovery on the sidelink.

Some techniques and apparatuses described herein provide for a pair ofnodes to perform beam failure detection and recovery on a sidelinkbetween the pair of nodes. For example, a pair of nodes associated withcommon timing may transmit signals between each other on resourceallocations known to the pair of nodes. The pair of nodes may identify ahealthy link or a failed beam or link based at least in part on whetherthe signals are received on the allocated resources, and may performbeam failure recovery (BFR) based at least in part on detecting a failedbeam or link. In this way, the pair of nodes can identify beam failureand perform BFR on a sidelink without the participation of a centralscheduler such as a gNB. Identifying beam failure and performing BFR onthe sidelink without the participation of the central scheduler mayreduce the impact of blocked beams, thereby improving radio linkquality, throughput, and resource utilization while reducing latency andoverhead associated with identifying failure of a beam or a sidelink.

FIGS. 5-8 are diagrams illustrating examples 500, 600, 700, and 800 ofsidelink beam failure detection and recovery, in accordance with variousaspects of the present disclosure. Examples 500, 600, 700, and 800include a first UE 120 and a second UE 120 (e.g., UE 305-1, UE 305-2, UE405, UE 410, and/or the like), which are referred to as the first UE andthe second UE. In some aspects, the first UE may be a first node and thesecond UE may be a second node. In some aspects, the first UE and/or thesecond UE may be associated with an access link to a BS 110. In someaspects, the first UE and the second UE may not be associated withaccess links to a BS 110. While the operations described in FIGS. 5-8are described as being performed by a first UE and a second UE, theseoperations can be performed by other types of wireless nodes (e.g., IABnodes and/or the like).

FIG. 5 shows an example 500 of sidelink beam monitoring on an intactsidelink. As shown, the first UE may be associated with a transmit (Tx)beam 505 and a receive (Rx) beam 510. The second UE may be associatedwith an Rx beam 515 corresponding to the Tx beam 505 and a Tx beam 520corresponding to the Rx beam 510. The Tx beam 505 and the Rx beam 515may form a beamformed sidelink 525 from the first UE to the second UE,and the Tx beam 520 and the Rx beam 510 may form a beamformed sidelink530 from the second UE to the first UE. For example, the beamformedsidelinks 525 and 530 may carry sidelink channels 310 (shown in FIG. 3)between the first UE and the second UE. In some aspects, the first UEand the second UE may be associated with a single beamformed sidelinkthat can be used for communicating in both directions, which is shown inFIG. 8.

As shown by reference number 535, the first UE may transmit a firstsignal at a time T1. For example, the first UE may transmit the firstsignal on a resource allocation (e.g., a time and/or frequency resourceallocation) known to the first UE and the second UE, wherein theresource allocation is associated with the time T1. The first UE and thesecond UE may be associated with common timing, meaning that the secondUE can determine the time T1 at which the UE transmits the first signal.For example, in some aspects, the first UE and the second UE may havecommon timing based at least in part on being configured with commontiming by a base station (e.g., via an access link). In some aspects,the first UE and the second UE may have common timing based at least inpart on respective positioning systems (e.g., Global Positioning System(GPS), Global Navigation Satellite System (GNSS), or the like) of thefirst UE and the second UE. By establishing common timing, the second UEcan determine when to expect the first signal (and the first UE candetermine when to expect the second signal) thereby enabling sidelinkbeam monitoring using the first signal, the second signal, and the thirdsignal.

In some aspects, the first UE and the second UE may determine T1, T2,and/or T3. For example, the first UE and the second UE may communicatewith each other to identify (e.g., determine) resource allocations fortransmission/reception of the first signal, the second signal, and thethird signal, which may eliminate the need for participation from ascheduling entity, thereby conserving computing resources of thescheduling entity. In some aspects, the first UE and the second UE maybe configured with information indicating T1, T2, and/or T3. Forexample, this information may be specified in a wirelesstelecommunication standard, which may conserve signaling resources ofthe UEs and a BS 110 associated with the UEs. In some aspects, the firstUE and the second UE may receive (e.g., from a scheduling entity such asa BS 110) information indicating T1, T2, and/or T3, which may conserveresources of the first UE and the second UE that would otherwise be usedto determine T1, T2, and/or T3.

As shown by reference number 540, the second UE may transmit, on thebeamformed sidelink 530, a second signal. For example, the second UE maytransmit the second signal at a time T2 (e.g., using a resourceallocation associated with the time T2 and known to the first UE and thesecond UE) based at least in part on receiving the first signal on theresource allocation associated with the time T1. In some aspects, T2 maybe offset from T1 by a length of time (e.g., approximately 10 ms and/orthe like), which may be configurable, predefined, negotiated by thefirst UE and the second UE, or the like. As shown by reference number545, the first UE may transmit, on the beamformed sidelink 525, a thirdsignal. For example, the first UE may transmit the third signal at atime T3 (e.g., using a resource allocation known to the first UE and thesecond UE and associated with the time T3) based at least in part onreceiving the second signal on the resource allocation associated withthe time T2. In some aspects, T3 may be offset from T2 by a length oftime (e.g., approximately 10 ms and/or the like), which may beconfigurable, predefined, negotiated by the first UE and the second UE,or the like.

By transmitting the second signal based at least in part on receivingthe first signal, and the third signal based at least in part onreceiving the second signal, the first UE and the second UE maydetermine whether or not the beamformed sidelink 525 and the beamformedsidelink 530 have failed. For examples of failure of the beamformedsidelink 525 and/or the beamformed sidelink 530, refer to FIGS. 6-8. Thefirst signal, the second signal, and/or the third signal may compriseany form of signaling, such as a reference signal (RS) (e.g., a channelstate information (CSI) RS (CSI-RS), a sounding reference signal, or thelike), a physical sidelink control channel (PSCCH), a physical sidelinkshared channel (PSSCH), a physical sidelink feedback channel (PSFCH),and/or the like. The first signal, the second signal, and the thirdsignal may all be the same type of signal or may include two or moredifferent types of signals.

Performing sidelink beam failure detection using the first signal, thesecond signal, and the third signal may involve lower overhead than someother sidelink beam failure detection procedures. For example, in somecases, a first UE may transmit a beacon (e.g., a signal such as asynchronization signal block and/or the like) on a beamformed sidelink,and a second UE may report to a base station 110 regarding whether thebeacon is received. The base station 110 may coordinate beam failurerecovery when the beacon is not received by the second UE. However, basestation coordination of monitoring and beam failure recovery may involvesignificant overhead and latency and may be difficult or impossible inpoor access network coverage scenarios. As another example, in somecases, a first UE may transmit a beacon on a beamformed sidelink, and asecond UE may initiate a random access channel (RACH) procedure on thebeamformed sidelink when the beacon is not received. However, theRACH-based sidelink beam failure detection procedure may require thatthe first UE and the second UE maintain RACH resources on an ongoingbasis, which may be more resource-intensive than maintaining resourcesfor the first signal, the second signal, and the third signal.

FIG. 6 shows an example 600 in which the beamformed sidelink from thefirst UE to the second UE has failed, as shown by the “X” on thebeamformed sidelink from the first UE to the second UE. As shown byreference number 610, the first UE may transmit the first signal at thetime T1. As shown by reference number 620, the second UE may determinethat the first signal is not received within a threshold time of T1.Accordingly, as shown by reference number 630, the second UE may nottransmit the second signal. As shown by reference number 640, the firstUE may determine that the second signal is not received at the time T2.This may indicate, to the first UE, that transmission of the firstsignal and/or the second signal has failed, meaning that one or more ofthe beamformed sidelinks between the first UE and the second UE hasfailed. Accordingly, as shown by reference number 650, the first UE maynot transmit the third signal at the time T3.

As shown by reference numbers 660 and 670, the first UE and the secondUE may perform a sidelink BFR procedure based at least in part ondetermining that the first signal, the second signal, and/or the thirdsignal are not received. In some aspects, the first UE and the second UEmay perform the sidelink BFR procedure based at least in part ondetermining that the first signal and the second signal are notreceived, which may reduce the latency associated with performing thesidelink BFR procedure relative to the case when the sidelink BFRprocedure is performed after determining that the third signal is notreceived.

In the sidelink BFR procedure, the first UE may transmit beam failurerecovery synchronization signals on multiple Tx beams at predeterminedtime/frequency locations (e.g., resource allocations) known to the firstUE and the second UE. The second UE may receive the beam failurerecovery synchronization signals on multiple Rx beams. Based at least inpart on receiving the beam failure recovery synchronization signals overmultiple Tx-Rx beam combinations, the second UE may determine the bestTx beam to be used by the first UE and the best Rx beam to be used bythe second UE for the beamformed sidelink from the first UE to thesecond UE. The second UE may use this information to transmit a RACHsignal to the first UE. For example, the RACH signal may use resourcesthat are configured as part of the sidelink BFR procedure. The first UEmay receive potential beam failure recovery RACH signals from the secondUE at predetermined time/frequency locations known to both UEs (e.g.,the RACH resources). The second UE may transmit the RACH signal at atime when the first UE is using the Rx beam corresponding to the best Txbeam that the first UE used to transmit the synchronization signal. Uponreceiving the RACH signal, the first UE may determine a best Tx beam forthe beamformed sidelink from the first UE to the second UE. Thissidelink BFR procedure may be initiated based at least in part onfailing to detect the first, second, and/or third signals (e.g., withoutintervention from a base station). It should also be noted that theroles of the first UE and the second UE in the sidelink BFR procedurecan be reversed (e.g., the first UE can perform the RACH procedure andthe second UE can transmit the synchronization signals) in order toestablish the beamformed link from the second UE to the first UE.

In some aspects, the first UE and/or the second UE may determine beamfailure based at least in part on failing to receive a threshold numberof signals. For example, the first UE and/or the second UE may declarebeam failure upon failing to receive N first/second/third signals, orupon determining that the procedure of receiving and transmitting thefirst/second/third signals has failed N times, where N is an integer.This may conserve computing and communication resources that wouldotherwise be used to premature trigger the sidelink BFR procedure due toa single failed signal transmission.

FIG. 7 shows an example 700 in which the beamformed sidelink from thesecond UE to the first UE has failed, as shown by the “X” on thebeamformed sidelink from the second UE to the first UE. As shown byreference number 710, the first UE may transmit the first signal at thetime T1. As shown by reference number 720, the second UE may transmitthe second signal at the time T2, based at least in part on successfullyreceiving the first signal at the time T1. However, the first UE failsto receive the second signal, as shown by reference number 730.Accordingly, the first UE determines that the third signal is not to betransmitted to the second UE, as shown by reference number 740. Thesecond UE may determine that the third signal is not received at thetime T3. Thus, the first UE and the second UE may determine that one ormore beamformed sidelinks between the second UE and the first UE havefailed, since the second UE successfully received the first signal andnot the third signal, and since the first UE did not receive the secondsignal. Thus, as shown by reference numbers 760 and 770, the first UEand the second UE may perform a sidelink BFR procedure, such as thesidelink BFR procedure described in connection with FIG. 6.

The case when both beamformed sidelinks fail may be similar to theexamples 600 and 700, since the first UE and the second UE may determinethat the third and second signals are not to be transmitted based atleast in part on failing to receive the second and first signals,respectively.

FIG. 8 shows an example 800 in which a single beamformed sidelinkbetween the second UE to the first UE is used. For example, the singlebeamformed sidelink may be a full duplex sidelink using some form ofduplexing or can be used to communicate in both directions. In example800, the beamformed sidelink has failed, as shown by the “X” on thebeamformed sidelink between the second UE and the first UE. Thus, thefirst signal shown by reference number 810 is not received by the secondUE, as shown by reference number 820. Accordingly, the second UEdetermines not to transmit the second signal, as shown by referencenumber 830. The first UE may determine that the second signal is notreceived at the time T2, as shown by reference number 840, and maydetermine that the third signal is not to be transmitted, as shown byreference number 850. As shown by reference numbers 860 and 870, thefirst UE and the second UE may perform a sidelink BFR procedure based atleast in part on determining that the beamformed sidelink has failed,such as the sidelink BFR procedure described in connection with FIG. 6.

As indicated above, FIGS. 5-8 are provided as one or more examples.Other examples may differ from what is described with respect to FIGS.5-8.

FIG. 9 is a diagram illustrating an example process 900 performed, forexample, by a first node, in accordance with various aspects of thepresent disclosure. Example process 900 is an example where the firstnode (e.g., UE 120, BS 110, UE 305, UE 405, UE 410, first UE 120 ofFIGS. 5-8, and/or the like) performs operations associated with sidelinkbeam failure detection.

As shown in FIG. 9, in some aspects, process 900 may includetransmitting, to a second node on a beamformed link from the first nodeto the second node, a first signal, wherein the first node and thesecond node are associated with common timing (block 910). For example,the first node (e.g., using controller/processor 280, transmit processor264, TX MIMO processor 266, MOD 254, antenna 252, controller/processor240, transmit processor 220, TX MIMO processor 230, MOD 232, antenna234, and/or the like) may transmit, to a second node on a beamformedlink from the first node to the second node, a first signal, asdescribed above. In some aspects, the first node and the second node areassociated with common timing.

As further shown in FIG. 9, in some aspects, process 900 may includedetermining whether a second signal, based at least in part on the firstsignal, is received on a beamformed link from the second node to thefirst node (block 920). For example, the first node (e.g., using antenna234, DEMOD 232, MIMO detector 236, receive processor 238,controller/processor 240, antenna 252, DEMOD 254, MIMO detector 256,receive processor 258, controller/processor 280, and/or the like) maydetermine whether a second signal, based at least in part on the firstsignal, is received on a beamformed link from the second node to thefirst node, as described above.

As further shown in FIG. 9, in some aspects, process 900 may includetransmitting a third signal on the beamformed link from the first nodeto the second node based at least in part on receiving the second signal(block 930). For example, the first node (e.g., usingcontroller/processor 280, transmit processor 264, TX MIMO processor 266,MOD 254, antenna 252, controller/processor 240, transmit processor 220,TX MIMO processor 230, MOD 232, antenna 234, and/or the like) maytransmit a third signal based at least in part on receiving the secondsignal, as described above.

As further shown in FIG. 9, in some aspects, process 900 may includeperforming a sidelink beam failure recovery procedure based at least inpart on determining that the second signal is not received (block 940).For example, the first node (e.g., using controller/processor 240,transmit processor 220, TX MIMO processor 230, MOD 232, antenna 234,controller/processor 280, transmit processor 264, TX MIMO processor 266,MOD 254, antenna 252, and/or the like) may perform a sidelink beamfailure recovery procedure based at least in part on determining thatthe second signal is not received, as described above.

Process 900 may include additional aspects, such as any single aspect orany combination of aspects described below and/or in connection with oneor more other processes described elsewhere herein.

In a first aspect, at least one of the first signal, the second signal,or the third signal comprise channel state information referencesignals.

In a second aspect, alone or in combination with the first aspect, thefirst signal, the second signal, and the third signal are associatedwith respective resource allocations that are known to the first nodeand the second node before transmission of the first signal.

In a third aspect, alone or in combination with one or more of the firstand second aspects, the respective resource allocations are determinedby one or more of the first node or the second node.

In a fourth aspect, alone or in combination with one or more of thefirst through third aspects, the respective resource allocations aredetermined by a base station associated with the first node or thesecond node.

In a fifth aspect, alone or in combination with one or more of the firstthrough fourth aspects, the beamformed link from the first node to thesecond node and the beamformed link from the second node to the firstnode are a same link.

In a sixth aspect, alone or in combination with one or more of the firstthrough fifth aspects, the common timing is determined based at least inpart on a base station associated with the first node and the secondnode.

In a seventh aspect, alone or in combination with one or more of thefirst through sixth aspects, the common timing is determined based atleast in part on positioning systems of the first node and the secondnode.

In an eighth aspect, alone or in combination with one or more of thefirst through seventh aspects, the beamformed link from the first nodeto the second node and the beamformed link from the second node to thefirst node are associated with a ProSe sidelink interface.

In a ninth aspect, alone or in combination with one or more of the firstthrough eighth aspects, the first node and the second node comprise userequipment.

In a tenth aspect, alone or in combination with one or more of the firstthrough ninth aspects, the first node and the second node compriseintegrated access and backhaul nodes.

In an eleventh aspect, alone or in combination with one or more of thefirst through tenth aspects, performing the sidelink beam failurerecovery procedure further comprises performing the sidelink beamfailure recovery procedure based at least in part on failing to receivethe second signal a threshold number of times.

Although FIG. 9 shows example blocks of process 900, in some aspects,process 900 may include additional blocks, fewer blocks, differentblocks, or differently arranged blocks than those depicted in FIG. 9.Additionally, or alternatively, two or more of the blocks of process 900may be performed in parallel.

FIG. 10 is a diagram illustrating an example process 1000 performed, forexample, by a second node, in accordance with various aspects of thepresent disclosure. Example process 1000 is an example where the secondnode (e.g., UE 120, BS 110, UE 305, UE 405, UE 410, second UE 120 ofFIGS. 5-8, and/or the like) performs operations associated with sidelinkbeam failure detection.

As shown in FIG. 10, in some aspects, process 1000 may includedetermining whether a first signal is received from a first node on abeamformed link from the first node to the second node, wherein thefirst node and the second node are associated with common timing (block1010). For example, the second node (e.g., using antenna 234, DEMOD 232,MIMO detector 236, receive processor 238, controller/processor 240,antenna 252, DEMOD 254, MIMO detector 256, receive processor 258,controller/processor 280, and/or the like) may determine whether a firstsignal is received from a first node on a beamformed link from the firstnode to the second node, as described above. In some aspects, the firstnode and the second node are associated with common timing.

As further shown in FIG. 10, in some aspects, process 1000 may includedetermining whether to transmit, on a beamformed link from the secondnode to the first node, a second signal based at least in part onwhether the first signal is received (block 1020). For example, thesecond node (e.g., using antenna 234, DEMOD 232, MIMO detector 236,receive processor 238, controller/processor 240, antenna 252, DEMOD 254,MIMO detector 256, receive processor 258, controller/processor 280,and/or the like) may determine whether to transmit, on a beamformed linkfrom the second node to the first node, a second signal based at leastin part on whether the first signal is received, as described above.

As further shown in FIG. 10, in some aspects, process 1000 may includereceiving a third signal on the beamformed link from the first node tothe second node based at least in part on the second signal (block1030). For example, the second node (e.g., using antenna 234, DEMOD 232,MIMO detector 236, receive processor 238, controller/processor 240,antenna 252, DEMOD 254, MIMO detector 256, receive processor 258,controller/processor 280, and/or the like) may receive a third signalbased at least in part on the second signal, as described above. In someaspects, the second node may receive the third signal after transmittingthe second signal.

As further shown in FIG. 10, in some aspects, process 1000 may includeperforming a sidelink beam failure recovery procedure based at least inpart on failing to receive the first signal or the third signal (block1040). For example, the second node (e.g., using antenna 234, DEMOD 232,MIMO detector 236, receive processor 238, controller/processor 240,antenna 252, DEMOD 254, MIMO detector 256, receive processor 258,controller/processor 280, and/or the like) may perform a sidelink beamfailure recovery procedure based at least in part on failing to receivethe first signal or the third signal, as described above. In someaspects, the second node may perform a sidelink beam failure recoveryprocedure after determining that the second signal is not to betransmitted.

Process 1000 may include additional aspects, such as any single aspector any combination of aspects described below and/or in connection withone or more other processes described elsewhere herein.

In a first aspect, process 1000 includes transmitting the second signalbased at least in part on receiving the first signal.

In a second aspect, alone or in combination with the first aspect, atleast one of the first signal, the second signal, or the third signalcomprise channel state information reference signals.

In a third aspect, alone or in combination with one or more of the firstand second aspects, the first signal, the second signal, and the thirdsignal are associated with respective resource allocations that areknown to the first node and the second node before transmission of thefirst signal.

In a fourth aspect, alone or in combination with one or more of thefirst through third aspects, the respective resource allocations aredetermined by one or more of the first node or the second node.

In a fifth aspect, alone or in combination with one or more of the firstthrough fourth aspects, the respective resource allocations aredetermined by a base station associated with the first node or thesecond node.

In a sixth aspect, alone or in combination with one or more of the firstthrough fifth aspects, the beamformed link from the first node to thesecond node and the beamformed link from the second node to the firstnode are a same link.

In a seventh aspect, alone or in combination with one or more of thefirst through sixth aspects, the common timing is based at least in parton a base station associated with the first node and the second node.

In an eighth aspect, alone or in combination with one or more of thefirst through seventh aspects, the common timing is based at least inpart on positioning systems of the first node and the second node.

In a ninth aspect, alone or in combination with one or more of the firstthrough eighth aspects, the beamformed link from the first node to thesecond node and the beamformed link from the second node to the firstnode are associated with a ProSe sidelink interface.

In a tenth aspect, alone or in combination with one or more of the firstthrough ninth aspects, the first node and the second node comprise userequipment.

In an eleventh aspect, alone or in combination with one or more of thefirst through tenth aspects, the first node and the second node compriseintegrated access and backhaul nodes.

In a twelfth aspect, alone or in combination with one or more of thefirst through eleventh aspects, performing the sidelink beam failurerecovery procedure further comprises performing the sidelink beamfailure recovery procedure based at least in part on failing to receiveone or more of the first signal or the third signal a threshold numberof times.

Although FIG. 10 shows example blocks of process 1000, in some aspects,process 1000 may include additional blocks, fewer blocks, differentblocks, or differently arranged blocks than those depicted in FIG. 10.Additionally, or alternatively, two or more of the blocks of process1000 may be performed in parallel.

The following provides an overview of some aspects of the presentdisclosure:

Aspect 1: A method of wireless communication performed by a first node,comprising: transmitting, to a second node on a beamformed link from thefirst node to the second node, a first signal, wherein the first nodeand the second node are associated with common timing; determiningwhether a second signal, based at least in part on the first signal, isreceived on a beamformed link from the second node to the first node;and transmitting a third signal on the beamformed link from the firstnode to the second node based at least in part on receiving the secondsignal; or performing a sidelink beam failure recovery procedure basedat least in part on determining that the second signal is not received.

Aspect 2: The method of aspect 1, wherein at least one of the firstsignal, the second signal, or the third signal comprise channel stateinformation reference signals.

Aspect 3: The method of any of aspects 1-2, wherein the first signal,the second signal, and the third signal are associated with respectiveresource allocations that are known to the first node and the secondnode before transmission of the first signal.

Aspect 4: The method of aspect 3, wherein the respective resourceallocations are determined by one or more of the first node or thesecond node.

Aspect 5: The method of aspect 3, wherein the respective resourceallocations are determined by a base station associated with the firstnode or the second node.

Aspect 6: The method of any of aspects 1-5, wherein the beamformed linkfrom the first node to the second node and the beamformed link from thesecond node to the first node are a same link.

Aspect 7: The method of any of aspects 1-6, wherein the common timing isdetermined based at least in part on a base station associated with thefirst node and the second node.

Aspect 8: The method of any of aspects 1-7, wherein the common timing isdetermined based at least in part on positioning systems of the firstnode and the second node.

Aspect 9: The method of any of aspects 1-8, wherein the beamformed linkfrom the first node to the second node and the beamformed link from thesecond node to the first node are associated with a ProSe sidelinkinterface.

Aspect 10: The method of any of aspects 1-9, wherein the first node andthe second node comprise user equipment.

Aspect 11: The method of any of aspects 1-9, wherein the first node andthe second node comprise integrated access and backhaul nodes.

Aspect 12: The method of any of aspects 1-11, wherein performing thesidelink beam failure recovery procedure further comprises performingthe sidelink beam failure recovery procedure based at least in part onfailing to receive the second signal a threshold number of times.

Aspect 13: A method of wireless communication performed by a secondnode, comprising: determining whether a first signal is received from afirst node on a beamformed link from the first node to the second node,wherein the first node and the second node are associated with commontiming; determining whether to transmit, on a beamformed link from thesecond node to the first node, a second signal based at least in part onwhether the first signal is received; and receiving a third signal basedat least in part on the second signal; or performing a sidelink beamfailure recovery procedure based at least in part on failing to receivethe first signal or the third signal.

Aspect 14: The method of aspect 13, further comprising transmitting thesecond signal based at least in part on receiving the first signal.

Aspect 15: The method of any of aspects 13-14, wherein at least one ofthe first signal, the second signal, or the third signal comprisechannel state information reference signals.

Aspect 16: The method of any of aspects 13-15, wherein the first signal,the second signal, and the third signal are associated with respectiveresource allocations that are known to the first node and the secondnode before transmission of the first signal.

Aspect 17: The method of aspect 16, wherein the respective resourceallocations are determined by one or more of the first node or thesecond node.

Aspect 18: The method of aspect 16, wherein the respective resourceallocations are determined by a base station associated with the firstnode or the second node.

Aspect 19: The method of any of aspects 13-18, wherein the beamformedlink from the first node to the second node and the beamformed link fromthe second node to the first node are a same link.

Aspect 20: The method of any of aspects 13-19, wherein the common timingis based at least in part on a base station associated with the firstnode and the second node.

Aspect 21: The method of any of aspects 13-20, wherein the common timingis based at least in part on positioning systems of the first node andthe second node.

Aspect 22: The method of any of aspects 13-21, wherein the beamformedlink from the first node to the second node and the beamformed link fromthe second node to the first node are associated with a ProSe sidelinkinterface.

Aspect 23: The method of any of aspects 13-22, wherein the first nodeand the second node comprise user equipment.

Aspect 24: The method of any of aspects 13-22, wherein the first nodeand the second node comprise integrated access and backhaul nodes.

Aspect 25: The method of any of aspects 13-24, wherein performing thesidelink beam failure recovery procedure further comprises: performingthe sidelink beam failure recovery procedure based at least in part onfailing to receive one or more of the first signal or the third signal athreshold number of times.

Aspect 26: An apparatus for wireless communication at a device,comprising a processor; memory coupled with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to perform the method of one or more aspects ofaspects 1-25.

Aspect 27: A device for wireless communication, comprising a memory andone or more processors coupled to the memory, the memory and the one ormore processors configured to perform the method of one or more aspectsof aspects 1-25.

Aspect 28: An apparatus for wireless communication, comprising at leastone means for performing the method of one or more aspects of aspects1-25.

Aspect 29: A non-transitory computer-readable medium storing code forwireless communication, the code comprising instructions executable by aprocessor to perform the method of one or more aspects of aspects 1-25.

Aspect 30: A non-transitory computer-readable medium storing a set ofinstructions for wireless communication, the set of instructionscomprising one or more instructions that, when executed by one or moreprocessors of a device, cause the device to perform the method of one ormore aspects of aspects 1-25.

The foregoing disclosure provides illustration and description, but isnot intended to be exhaustive or to limit the aspects to the preciseform disclosed. Modifications and variations may be made in light of theabove disclosure or may be acquired from practice of the aspects.

As used herein, the term “component” is intended to be broadly construedas hardware, firmware, and/or a combination of hardware and software. Asused herein, a processor is implemented in hardware, firmware, and/or acombination of hardware and software.

As used herein, satisfying a threshold may, depending on the context,refer to a value being greater than the threshold, greater than or equalto the threshold, less than the threshold, less than or equal to thethreshold, equal to the threshold, not equal to the threshold, and/orthe like.

It will be apparent that systems and/or methods described herein may beimplemented in different forms of hardware, firmware, and/or acombination of hardware and software. The actual specialized controlhardware or software code used to implement these systems and/or methodsis not limiting of the aspects. Thus, the operation and behavior of thesystems and/or methods were described herein without reference tospecific software code—it being understood that software and hardwarecan be designed to implement the systems and/or methods based, at leastin part, on the description herein.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the disclosure of various aspects. In fact, many ofthese features may be combined in ways not specifically recited in theclaims and/or disclosed in the specification. Although each dependentclaim listed below may directly depend on only one claim, the disclosureof various aspects includes each dependent claim in combination withevery other claim in the claim set. A phrase referring to “at least oneof” a list of items refers to any combination of those items, includingsingle members. As an example, “at least one of: a, b, or c” is intendedto cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combinationwith multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c,a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering ofa, b, and c).

No element, act, or instruction used herein should be construed ascritical or essential unless explicitly described as such. Also, as usedherein, the articles “a” and “an” are intended to include one or moreitems, and may be used interchangeably with “one or more.” Furthermore,as used herein, the terms “set” and “group” are intended to include oneor more items (e.g., related items, unrelated items, a combination ofrelated and unrelated items, and/or the like), and may be usedinterchangeably with “one or more.” Where only one item is intended, thephrase “only one” or similar language is used. Also, as used herein, theterms “has,” “have,” “having,” and/or the like are intended to beopen-ended terms. Further, the phrase “based on” is intended to mean“based, at least in part, on” unless explicitly stated otherwise.

What is claimed is:
 1. A first node for wireless communication,comprising: a memory; and one or more processors operatively coupled tothe memory, the one or more processors configured to: transmit, to asecond node on a beamformed link from the first node to the second node,a first signal, wherein the first node and the second node areassociated with common timing; determine whether a second signal, basedat least in part on the first signal, is received on a beamformed linkfrom the second node to the first node; and transmit a third signal onthe beamformed link from the first node to the second node based atleast in part on receiving the second signal; or perform a sidelink beamfailure recovery procedure based at least in part on determining thatthe second signal is not received.
 2. The first node of claim 1, whereinat least one of the first signal, the second signal, or the third signalcomprise channel state information reference signals.
 3. The first nodeof claim 1, wherein the first signal, the second signal, and the thirdsignal are associated with respective resource allocations that areknown to the first node and the second node before transmission of thefirst signal.
 4. The first node of claim 3, wherein the respectiveresource allocations are determined by one or more of the first node orthe second node.
 5. The first node of claim 3, wherein the respectiveresource allocations are determined by a base station associated withthe first node or the second node.
 6. The first node of claim 1, whereinthe beamformed link from the first node to the second node and thebeamformed link from the second node to the first node are a same link.7. The first node of claim 1, wherein the common timing is determinedbased at least in part on a base station associated with the first nodeand the second node.
 8. The first node of claim 1, wherein the commontiming is determined based at least in part on positioning systems ofthe first node and the second node.
 9. The first node of claim 1,wherein the beamformed link from the first node to the second node andthe beamformed link from the second node to the first node areassociated with a ProSe sidelink interface.
 10. The first node of claim1, wherein the first node and the second node comprise user equipment.11. The first node of claim 1, wherein the first node and the secondnode comprise integrated access and backhaul nodes.
 12. The first nodeof claim 1, wherein the one or more processors, when performing thesidelink beam failure recovery procedure, are configured to perform thesidelink beam failure recovery procedure based at least in part onfailing to receive the second signal a threshold number of times.
 13. Asecond node for wireless communication, comprising: a memory; and one ormore processors operatively coupled to the memory, the one or moreprocessors configured to: determine whether a first signal is receivedfrom a first node on a beamformed link from the first node to the secondnode, wherein the first node and the second node are associated withcommon timing; determine whether to transmit, on a beamformed link fromthe second node to the first node, a second signal based at least inpart on whether the first signal is received; and receive a third signalbased at least in part on the second signal; or perform a sidelink beamfailure recovery procedure based at least in part on failing to receivethe first signal or the third signal.
 14. The second node of claim 13,wherein the one or more processors are further configured to transmitthe second signal based at least in part on receiving the first signal.15. The second node of claim 13, wherein the beamformed link from thefirst node to the second node and the beamformed link from the secondnode to the first node are a same link.
 16. The second node of claim 13,wherein the beamformed link from the first node to the second node andthe beamformed link from the second node to the first node areassociated with a ProSe sidelink interface.
 17. The second node of claim13, wherein the one or more processors, when performing the sidelinkbeam failure recovery procedure, are configured to: perform the sidelinkbeam failure recovery procedure based at least in part on failing toreceive one or more of the first signal or the third signal a thresholdnumber of times.
 18. A method of wireless communication performed by afirst node, comprising: transmitting, to a second node on a beamformedlink from the first node to the second node, a first signal, wherein thefirst node and the second node are associated with common timing;determining whether a second signal, based at least in part on the firstsignal, is received on a beamformed link from the second node to thefirst node; and transmitting a third signal on the beamformed link fromthe first node to the second node based at least in part on receivingthe second signal; or performing a sidelink beam failure recoveryprocedure based at least in part on determining that the second signalis not received.
 19. The method of claim 18, wherein at least one of thefirst signal, the second signal, or the third signal comprise channelstate information reference signals.
 20. The method of claim 18, whereinthe first signal, the second signal, and the third signal are associatedwith respective resource allocations that are known to the first nodeand the second node before transmission of the first signal.
 21. Themethod of claim 18, wherein the beamformed link from the first node tothe second node and the beamformed link from the second node to thefirst node are a same link.
 22. The method of claim 18, wherein thebeamformed link from the first node to the second node and thebeamformed link from the second node to the first node are associatedwith a ProSe sidelink interface.
 23. The method of claim 18, whereinperforming the sidelink beam failure recovery procedure furthercomprises performing the sidelink beam failure recovery procedure basedat least in part on failing to receive the second signal a thresholdnumber of times.
 24. A method of wireless communication performed by asecond node, comprising: determining whether a first signal is receivedfrom a first node on a beamformed link from the first node to the secondnode, wherein the first node and the second node are associated withcommon timing; determining whether to transmit, on a beamformed linkfrom the second node to the first node, a second signal based at leastin part on whether the first signal is received; and receiving a thirdsignal based at least in part on the second signal; or performing asidelink beam failure recovery procedure based at least in part onfailing to receive the first signal or the third signal.
 25. The methodof claim 24, further comprising transmitting the second signal based atleast in part on receiving the first signal.
 26. The method of claim 24,wherein the beamformed link from the first node to the second node andthe beamformed link from the second node to the first node are a samelink.
 27. The method of claim 24, wherein the beamformed link from thefirst node to the second node and the beamformed link from the secondnode to the first node are associated with a ProSe sidelink interface.28. The method of claim 24, wherein the first node and the second nodecomprise user equipment.
 29. The method of claim 24, wherein the firstnode and the second node comprise integrated access and backhaul nodes.30. The method of claim 24, wherein performing the sidelink beam failurerecovery procedure further comprises: performing the sidelink beamfailure recovery procedure based at least in part on failing to receiveone or more of the first signal or the third signal a threshold numberof times.